Preparation method of nervonic acid composite nano-emulsion and nervonic acid composite nano-emulsion prepared by same

Abstract

The invention discloses a preparation method of a nervonic acid composite nano-emulsion and the nervonic acid composite nano-emulsion prepared by the preparation method. The prepared nervonic acid composite nano-emulsion is small in particle size, good in emulsifying effect, excellent in stability, good in taste and suitable for long-term storage, development of the shiny-leaved yellowhorn industry can be promoted, the nervonic acid composite nano-emulsion can be applied to the field of food and used for supplementing nervonic acid needed by the human body, and ethyl nervonic acid is stable in structure and beneficial to storage and transportation.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a method for purifying nervonic acid in *Sapindus mukorossi* oil and the preparation of its composite nanoemulsion. Background Technology

[0002] Nervonic acid, or cis-15-tatracosanic acid (NA), is a long-chain monounsaturated fatty acid (MUFA). It binds to sphingosine via an amide bond to form sphingolipids, which are essential components of the brain's white matter and myelinated nerve fibers. Studies have shown that a deficiency of nervonic acid in the brain can cause brain damage and memory loss, leading to stroke sequelae, Alzheimer's disease, and other brain disorders. Nervonic acid is also an important component of biological membranes, playing a vital role in the binding of neurotransmitters and receptors, ensuring timely information transmission in the brain, accelerating information transmission between nerve cells, promoting nerve cell regeneration and contact inhibition, thereby improving brain function, preventing brain aging and Alzheimer's disease, and enhancing memory. Therefore, nervonic acid can supplement brain nutrition, repair brain damage, benefit infant brain development, enhance memory, delay aging, and prevent and treat Alzheimer's disease; it is known by scientists as "brain gold." Furthermore, nervonic acid is very expensive, costing up to three times the price of gold.

[0003] Patent CN103396304A describes a method for chemically synthesizing nervonic acid using methyl cis-13-docosahexaenoate as a raw material. However, this patent uses phosphorus trichloride, which is environmentally harmful, as the chlorination reagent during the chlorination reaction, and traditional diethyl malonate as a raw material in the carbonization reaction, significantly reducing the atom utilization rate of the method. Patent CN111423320A describes a method for chemically synthesizing nervonic acid using erucic acid as a raw material. Patent CN1609090A uses silica gel column adsorption of nervonic acid, followed by elution with a special eluent to obtain nervonic acid with a purity of over 90%. However, these methods suffer from high equipment costs, long separation and purification routes, complex chemical synthesis routes and processes for nervonic acid, and low yields, limiting the large-scale production of high-purity nervonic acid and its derivatives.

[0004] *Xanthoceras sorbifolium*, a shrub or deciduous small tree belonging to the Sapindaceae family, is mainly distributed in northern my country. The seeds contain approximately 35% oil, while the kernels contain over 60%, with linoleic acid and oleic acid, essential for the human body, accounting for about three-quarters of the total oil content, earning it the title of "liquid gold." Nutritionally, *Xanthoceras sorbifolium* oil is an edible vegetable oil rich in unsaturated fatty acids (up to 94%). In addition to oleic and linoleic acids, it also contains approximately 3% nervonic acid. Therefore, developing a method for efficiently extracting nervonic acid from *Xanthoceras sorbifolium* oil is of practical significance in addressing the problems of high production costs, complex operations, and low extraction purity in existing technologies. Summary of the Invention

[0005] This invention provides a method for preparing a nervonic acid composite nanoemulsion, comprising the following steps: Solution A was prepared by adding Xanthoceras sorbifolium protein to water and stirring at room temperature until dissolved. Solution B was prepared by dissolving maltodextrin and carrageenan in water and stirring at room temperature until dissolved. Solution B was slowly added to solution A and homogenized at high speed to obtain solution C. Ethyl nervonic acid was added to Xanthoceras sorbifolium oil and homogenized at high speed to obtain solution D. Under high-speed homogenization conditions, solution D was gradually added to solution C to obtain a nervonic acid composite nanoemulsion. Based on the above method, the mass fraction of each component in the total water used in the nervonic acid composite nanoemulsion is as follows: The ingredients include 0.5-6% Xanthoceras sorbifolium protein, 0.1-0.5% maltodextrin, 0.1-0.5% carrageenan, 10-40% nervonic acid ethyl ester, and 2-10% Xanthoceras sorbifolium oil.

[0006] Based on the above method, the nervonic acid ethyl ester is prepared by the following method: nervonic acid crystals are mixed with a 2% sulfuric acid-ethanol solution and subjected to ethyl esterification in a 60°C water bath to obtain nervonic acid ethyl ester.

[0007] Based on the above method, the preparation method of the nervonic acid crystals is as follows: (1) Saponification Saponification was carried out by adding *Sapindus mukorossi* oil to a NaOH-ethanol solution and stirring in a water bath. (2) Layering After saponification is complete, petroleum ether is added to remove unsaponifiables, followed by acidification. The solution is then stirred in a water bath until distinct layers are formed, with the upper layer being a clear fatty acid layer and the lower layer being an aqueous layer containing glycerol. (3) Concentration The layered solution was transferred to a separatory funnel, allowed to stand, the aqueous layer was removed, the fatty acid layer was washed with water until neutral, dried to remove water, filtered under reduced pressure, and petroleum ether was recovered to obtain nervonic acid concentrate. (4) Distillation The nervonic acid concentrate was subjected to molecular distillation to obtain the nervonic acid isolate from the heavy phase. (5) Low-temperature crystallization The nervonic acid isolate was added to anhydrous ethanol and crystallized at low temperature; after crystallization, it was quickly filtered. (6) recrystallization The crystals were redissolved in anhydrous ethanol and recrystallized at low temperature. After recrystallization, the mixture was quickly filtered to obtain solid nervonic acid crystals.

[0008] Based on the above method, the mass-to-volume ratio of *Sapindus mukorossi* oil to NaOH-ethanol solution is selected from 1:5 to 8, g:mL; the concentration of the NaOH-ethanol solution is selected from 0.5 to 1.5M.

[0009] Based on the above method, the conditions for water bath stirring are all selected from: stirring in a water bath at 70~85℃ for 0.5~2h.

[0010] Based on the above method, the acidification treatment is as follows: sulfuric acid is added to adjust the pH of the system to 2-3.

[0011] Based on the above method, the distillation conditions are selected from: a pressure of 1×10⁻⁶. -2 ~1×10 -3 mbar, temperature 130~150℃.

[0012] Based on the above method, the mass-to-volume ratio of nervonic acid isolate to anhydrous ethanol is selected from 1:4 to 8, g:mL; the mass-to-volume ratio of crystals to anhydrous ethanol is selected from 1:4 to 8, g:mL.

[0013] This invention provides a nervonic acid composite nanoemulsion prepared by the above method.

[0014] The beneficial effects of this invention are as follows: This invention utilizes the different molecular free paths of various fatty acids in *Xanthoceras sorbifolium* oil, employing temperature and pressure variations to alter the physical form of nervonic acid. This ultimately achieves the separation and purification of nervonic acid from other fatty acids, resulting in high nervonic acid extraction rate and purity, low erucic acid content, and a simple, efficient extraction process with few and low-cost reagents. Furthermore, the nervonic acid composite nanoemulsion prepared by this invention exhibits small particle size, excellent emulsification effect, superior stability, and a pleasant taste, making it suitable for long-term storage. This not only promotes the development of the *Xanthoceras sorbifolium* industry but also has applications in the food sector, supplementing the human body with nervonic acid. Moreover, the stable structure of nervonic acid ethyl ester facilitates preservation and transportation. Attached Figure Description

[0015] Figure 1 Layering effect of nervonic acid composite nanoemulsions prepared for different proteins on day 0; where A is soybean protein, B is peanut protein, and C is Xanthoceras sorbifolium protein; Figure 2 Layering effect of nervonic acid composite nanoemulsions prepared for different proteins on day 20; where A is soybean protein, B is peanut protein, and C is Xanthoceras sorbifolium protein. Detailed Implementation

[0016] In this invention, the *Sapindus mukorossi* oil is obtained through commercial channels.

[0017] In this invention, the *Xanthoceras sorbifolium* protein is prepared by defatting and then ultra-finely pulverizing the kernel of *Xanthoceras sorbifolium*, with a protein content of 50%. Defatting is a conventional and commonly used defatting technique.

[0018] Other materials used in this invention, unless otherwise stated, are commercially available. Other terms used in this invention, unless otherwise specified, generally have the meanings commonly understood by those skilled in the art. The invention is further described in detail below with reference to specific embodiments and data. The following embodiments are merely illustrative and not intended to limit the scope of the invention in any way.

[0019] Example 1 The extraction steps for nervonic acid from *Sapindus mukorossi* oil are as follows: Step 1: Weigh 30g of Xanthoceras sorbifolium oil and add it to 1M NaOH-ethanol solution at a ratio of 1:5 (g:mL). Saponify the solution by stirring in a water bath at 80℃ for 1 hour.

[0020] Step 2: After saponification is complete, add petroleum ether to remove unsaponifiables, and add 10% sulfuric acid to adjust the pH to 2-3. Stir in a water bath at 80℃ for 1 hour until the solution is clearly separated into layers, with the upper layer being a clear fatty acid layer and the lower layer being an aqueous layer containing glycerol.

[0021] Step 3: Transfer the solution to a separatory funnel, let it stand, remove the water layer, wash the fatty acid layer with water until neutral, add anhydrous sodium sulfate to dry the trace amounts of water, filter under reduced pressure, and rotary evaporate at 70°C to recover petroleum ether, obtaining 24.8g of nervonic acid concentrate.

[0022] Step 4: Place the nervonic acid concentrate under a pressure of 1.8 × 10⁻⁶. -3 Under conditions of mbar and 150℃, since the mean free path of vapor molecules is greater than the distance between the evaporation surface and the condensation surface, and the evaporation time required for each component is different, nervonic acid can be further purified. After the heavy phase of molecular distillation flows out and after three-stage molecular distillation, about 2.1g of nervonic acid isolate is obtained, in which the purity of nervonic acid at this time is 33.8%.

[0023] When a sample is subjected to molecular distillation, it will produce a light phase and a heavy phase. When the liquid mixture flows along the heating plate and is heated, light and heavy molecules will escape from the liquid surface and enter the gas phase. Since the free path of light and heavy molecules is different, the molecules of different substances will travel different distances after escaping from the liquid surface. If a condenser plate is set up properly, the light molecules will reach the condenser plate and be condensed and discharged, while the heavy molecules will not reach the condenser plate and will be discharged along the mixture.

[0024] Under the above distillation conditions, three-stage molecular distillation can be achieved. The first-stage molecular distillation removes some C16-C18 fatty acids such as palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid. The second-stage molecular distillation removes palmitic acid, stearic acid, and most of the C18 unsaturated fatty acids such as oleic acid and linoleic acid. The third-stage molecular distillation removes C18-C22 fatty acids. Finally, nervonic acid is concentrated, separated from other substances, and flows out from the heavy phase.

[0025] Step 5: Continue to collect the product from step 4. Take 10g of the product from step 4 and add anhydrous ethanol at a ratio of 1:5 (g:mL). Keep the mixture at -20℃ and 0.1 bar for 3h to carry out low-temperature crystallization. Then place it under 0.8 bar and filter it quickly.

[0026] Step 6: Repeat the process of adding anhydrous ethanol to the crystals from Step 5 at a ratio of 1:5 (g:mL) to reconstitute the crystals, and continue to maintain the solution at -20℃ and 0.1 bar for 3 hours to recrystallize at low temperature; then place the solution at 0.8 bar and filter rapidly to obtain 4.1g of solid nervonic acid crystals.

[0027] The purity of nervonic acid in the crystals was determined to be 84%, and the erucic acid content was 1.3%, which means that the extraction rate of nervonic acid was 80%.

[0028] Animal experiments have shown that excessive intake of edible oils high in erucic acid can lead to myocardial fibrosis and cardiomyopathy, causing thickening of blood vessel walls and fat deposition in the myocardium; it can also cause slow weight gain and poor development in animals; if the erucic acid content in the feed of experimental male rats reaches 10%, phenomena such as smaller testes and no mature sperm will occur, resulting in decreased fertility; in addition, erucic acid can also cause a decrease in platelets.

[0029] I. Exploration of Molecular Distillation Conditions Using the technical solution of Example 1 as a standard, the purity changes of nervonic acid (NA) in the nervonic acid isolate obtained under different temperature and pressure treatment conditions in molecular distillation (step four) were studied. The results are shown in Table 1 below.

[0030] Table 1. Changes in nervonic acid purity among nervonic acid isolates under different temperatures and pressures. Table 1 shows that changes in temperature and pressure during molecular distillation significantly alter the purity of nervonic acid extracted from *Xanthoceras sorbifolium*. When the molecular distillation conditions are 150℃ and 1.8 × 10⁻⁶, the purity of nervonic acid significantly changes. -3 At mbar, the purity of nervonic acid in the obtained nervonic acid isolate is the highest, which is therefore the optimal condition for molecular distillation.

[0031] II. Exploration of Low-Temperature Crystallization Conditions Using the technical solution of Example 1 as the standard, the effects of different temperature conditions, with and without pressure, on the purity of nervonic acid and the content of erucic acid during low-temperature crystallization (steps 5 and 6) were studied. The results are shown in Table 2 below.

[0032] Table 2. Changes in nervonic acid purity and erucic acid content under different temperature and pressure conditions. Table 2 shows that without pressure, the low-temperature crystallization effect is worse, resulting in lower nervonic acid purity and higher erucic acid content. However, under pressure, setting the crystallization temperature to -20℃ can achieve a nervonic acid purity of 84% and an erucic acid content as low as 1.3%.

[0033] Example 2 Preparation of nervonic acid ethyl ester: The ethyl esterification of nervonic acid crystals was carried out using the sulfuric acid-ethanol esterification method.

[0034] The nervonic acid crystal sample was added to a 1% sulfuric acid-ethanol solution at a ratio of 1:40 (g / mL), heated in a water bath at 65°C for 40 min, cooled, and then hexane and distilled water were added at a ratio of 1:40 (g / mL), mixed well, and the supernatant was collected and concentrated under reduced pressure to obtain nervonic acid ethyl ester.

[0035] Example 3 The preparation steps of the nervonic acid composite nanoemulsion are as follows: Step 1: Add the *Sapindus mukorossi* protein (0.5g, 1g, 1.5g, 2g, 2.5g, 3g, 3.5g, 4g, 4.5g, 5g, 5.5g, and 6g respectively) to 70mL of deionized water and stir with an electromagnetic heating stirrer for 20 minutes at room temperature until completely dissolved to prepare solution A.

[0036] Step 2: Dissolve 0.1g of maltodextrin and 0.1g of carrageenan in 30mL of deionized water in sequence, and stir with an electromagnetic heating stirrer for 10min at room temperature until completely dissolved to obtain solution B.

[0037] Step 3: Slowly add solution B to solution A and homogenize for 2 minutes in a high-speed homogenizer at 13000 r / min to obtain solution C (aqueous phase).

[0038] Step 4: Weigh 10g of Xanthoceras sorbifolium oil, add 30g of ethyl nervate to the Xanthoceras sorbifolium oil, homogenize in a high-speed homogenizer for 2 minutes to obtain solution D (oil phase).

[0039] Step 5: In a high-speed homogenizer at 13000 r / min, gradually add solution D to solution C and maintain the homogenization process for 4 min to finally obtain nervonic acid composite nanoemulsion.

[0040] In the preparation of the above-mentioned nervonic acid composite nanoemulsion, the total volume of deionized water used was 100 mL. Therefore, the proportion of Chinese crown fruit protein used to the amount of deionized water in each group was 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, and 6.0%, respectively.

[0041] III. The Influence of Protein Type on Emulsion Stability The effects of different proteins on the stability of nervonic acid composite nanoemulsions were investigated, and the experiments were conducted as follows: Nervonic acid composite nanoemulsions were prepared using soybean protein, peanut protein, and *Sapindus mukorossi* protein, respectively, with soybean protein and peanut protein being commercially available.

[0042] Step 1: Add 3g of soy protein, peanut protein, and *Sapindus mukorossi* protein to 100mL of deionized water respectively, and stir with an electromagnetic heating stirrer for 20 minutes at room temperature until completely dissolved to prepare solution A.

[0043] Step 2: Weigh 10g of *Sapindus mukorossi* oil, add 5g of ethyl nervate to the *Sapindus mukorossi* oil, homogenize in a high-speed homogenizer for 2 minutes to obtain solution B.

[0044] Step 3: Under the condition of 13000r / min in a high-speed homogenizer, solution B is slowly added to solution A and homogenized for 4min to finally obtain nervonic acid composite nanoemulsion, which is then stored at 4℃.

[0045] Observe the stability of nervonic acid composite nanoemulsions prepared from different proteins, such as Figure 1 and Figure 2 As shown: The separation time of each composite nanoemulsion was as follows: peanut protein < soybean protein < *Xanthoceras sorbifolium* protein (separation times were 7 days, 12 days, and 20 days, respectively). This indicates that soybean protein and peanut protein separated more quickly than *Xanthoceras sorbifolium* protein. Therefore, the composite nanoemulsions prepared from the other two proteins showed poorer stability compared to *Xanthoceras sorbifolium* protein, leading to the selection of *Xanthoceras sorbifolium* protein for preparing the nanoemulsion.

[0046] IV. Performance Testing of Nervonic Acid Composite Nanoemulsion The average particle size, polydispersity index (PDI), and zeta potential of the nervonic acid composite nanoemulsion in Example 2 were determined using a Malvern Zetasizer Nano ZS90 nanoparticle size and zeta potential analyzer. Each sample was measured three times.

[0047] The test results are shown in Table 3: Table 3 Performance test results of nervonic acid composite nanoemulsion As shown in Table 3, by adjusting the proportion of *Xanthoceras sorbifolium* protein in the aqueous phase, and considering particle size, PDI number, and zeta potential, the particle size is smallest and the absolute value of the zeta potential is closer to 0 when the proportion of *Xanthoceras sorbifolium* protein is 3.5%. Therefore, the emulsion prepared with 3.5% *Xanthoceras sorbifolium* protein exhibits the best performance.

[0048] Based on the above results, the product prepared with 3.5% Xanthoceras sorbifolium protein is more in line with the requirements. Therefore, it can be determined that 3.5% Xanthoceras sorbifolium protein in the aqueous phase is the optimal formula for actual production.

[0049] Application examples Scale up the production process to prepare nervonic acid composite nanoemulsion: Step 1: Add 350g of Xanthoceras sorbifolium protein to 7L of deionized water and stir with a stirrer for 20 minutes at room temperature until completely dissolved to make solution A. Store at room temperature.

[0050] Step 2: Dissolve 10g of maltodextrin and 10g of carrageenan in 3L of deionized water in sequence, stir at room temperature for 20 minutes until completely dissolved, to obtain solution B.

[0051] Step 3: Slowly add solution B to solution A and homogenize for 20 minutes at 13000 r / min in a high-speed homogenizer to obtain solution C (aqueous phase).

[0052] Step 4: Weigh 1000g of *Sapindus mukorossi* oil, add 3000g of ethyl nervate to the *Sapindus mukorossi* oil, and homogenize for 30 minutes in a high-speed homogenizer to obtain solution D.

[0053] Step 5: Solution C is gradually added to solution D in a high-speed homogenizer at 13000 r / min, and the homogenization process is maintained for 40 min. The final product is a nervonic acid composite nanoemulsion.

[0054] Step 6: Fill the nervonic acid composite nanoemulsion product into sterilized glass bottles and store them in a cool, dry place in a sealed container.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a nervonic acid composite nanoemulsion, characterized in that, The steps include: adding *Sapindus mukorossi* protein to water and stirring at room temperature until dissolved to prepare solution A; dissolving maltodextrin and carrageenan in water and stirring at room temperature until dissolved to obtain solution B; slowly adding solution B to solution A and homogenizing at high speed to obtain solution C; adding ethyl nervate to *Sapindus mukorossi* oil and homogenizing at high speed to obtain solution D; Under high-speed homogenization conditions, solution D was gradually added to solution C to obtain a nervonic acid composite nanoemulsion.

2. The preparation method according to claim 1, characterized in that, The mass fraction of each component in the total water used in the nervonic acid composite nanoemulsion is shown below: The ingredients include 0.5-6% Xanthoceras sorbifolium protein, 0.1-0.5% maltodextrin, 0.1-0.5% carrageenan, 10-40% nervonic acid ethyl ester, and 2-10% Xanthoceras sorbifolium oil.

3. The preparation method according to claim 1, characterized in that, The nervonic acid ethyl ester is prepared by the following method: nervonic acid crystals are mixed with a 2% sulfuric acid-ethanol solution and subjected to ethyl esterification in a 60°C water bath to obtain nervonic acid ethyl ester.

4. The preparation method according to claim 3, characterized in that, The method for preparing the nervonic acid crystals is as follows: (1) Saponification Saponification was carried out by adding *Sapindus mukorossi* oil to a NaOH-ethanol solution and stirring in a water bath. (2) Layering After saponification is complete, petroleum ether is added to remove unsaponifiables, followed by acidification. The solution is then stirred in a water bath until distinct layers are formed, with the upper layer being a clear fatty acid layer and the lower layer being an aqueous layer containing glycerol. (3) Concentration The layered solution was transferred to a separatory funnel, allowed to stand, the aqueous layer was removed, the fatty acid layer was washed with water until neutral, dried to remove water, filtered under reduced pressure, and petroleum ether was recovered to obtain nervonic acid concentrate. (4) Distillation The nervonic acid concentrate was subjected to molecular distillation to obtain the nervonic acid isolate from the heavy phase. (5) Low-temperature crystallization The nervonic acid isolate was added to anhydrous ethanol and crystallized at low temperature. After crystallization, filter quickly. (6) recrystallization The crystals were redissolved in anhydrous ethanol and recrystallized at low temperature. After recrystallization, the mixture was quickly filtered to obtain solid nervonic acid crystals.

5. The preparation method according to claim 4, characterized in that, The mass-to-volume ratio of *Sapindus mukorossi* oil to NaOH-ethanol solution is selected from 1:5 to 8, g:mL; the concentration of the NaOH-ethanol solution is selected from 0.5 to 1.5M.

6. The preparation method according to claim 4, characterized in that, The conditions for water bath stirring are all selected from: stirring in a water bath at 70~85℃ for 0.5~2h.

7. The preparation method according to claim 4, characterized in that, The acidification process involves adding sulfuric acid to adjust the pH of the system to 2-3.

8. The preparation method according to claim 4, characterized in that, The distillation conditions are selected from: a pressure of 1×10⁻⁶. -2 ~1×10 -3 mbar, temperature 130~150℃.

9. The preparation method according to claim 4, characterized in that, The mass-to-volume ratio of nervonic acid isolate to anhydrous ethanol was selected from 1:4 to 8, g:mL; the mass-to-volume ratio of crystals to anhydrous ethanol was selected from 1:4 to 8, g:mL.

10. The nervonic acid composite nanoemulsion prepared by the method according to any one of claims 1-9.

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